1. Field of the Invention
The present invention relates to a thread-wound golf ball having excellent scuff resistance when hit with an iron club, and improved spin, feel, and distance upon a full shot with a driver.
2. Prior Art
Many thread-wound golf balls in which the cover has a two-layer construction have been proposed in an effort to improve the spin, feel, and distance of thread-wound golf balls. For example, JP-A 224323/1996 discloses a thread-wound golf ball in which the outer cover layer is given a lower hardness than the inner cover layer to enhance spin and provide a softer feel when the ball is shot with an iron. These thread-wound golf balls typically use ionomer resins as the cover stock. Low-hardness ionomer resins are subject to abrasion and cutting when shot with an iron and also have low rebound characteristics.
The covers on thread-wound golf balls are generally compression molded on account of the low heat resistance of the rubber thread. The compression molding operation uses a molding press which is provided with a plurality of mold cavities to achieve better productivity. Due to disparities such as temperature variations on the surface of the press platen and variations in the machined precision of the mold cavities, the thread-wound golf balls as molded exhibit a large variation in diameter and a low sphericity compared with injection-molded solid golf balls. Moreover, because the molding press is provided with a larger number of cavities than for injection molding, compression molding entails greater expense.
Furthermore, the cover stock in conventional thread-wound golf balls penetrates into gaps and voids in the rubber thread layer, thereby improving adhesion between the rubber thread layer and the cover and assuring durability of the golf ball to repeated impact. Yet, the rubber thread may be cut if the ball is topped with an iron, resulting in deformation of the ball.